Data corruption after moving directories

While investigating CORE-11377, I ran into multiple issues related to renaming a directory, and then moving a subdirectory back to the original location.

updatedir.c which reproduces this issue, creates two directories, each with a testfile:

c:\movetest\1\

c:\movetest\1\test.txt

c:\movetest\1\u\

c:\movetest\1\u\test.txt

First it renames c:\movetest\1 into c:\movetest\2.
Next it moves c:\movetest\2\u back to c:\movetest\1.

The main problem is a data corruption after doing this. I'll add more details below.